I've only used PPC based software so I don't know if I can help w/ you Iphone. Try going to JBM ballistics and use the "litz" bullet profile. I'd set your Iphone to match that profile as closely as possible on your Iphone. To get it all right, you have to be certain your input to the program is all correct. Muzzle velocity isn't what your chrony reads, it's the actual velocity at the muzzle. As long as you measure the distance from your muzzle to your chrony and use that w/ JBM it will give you your true MV.

there is also a range at ridgeway pa. n.c. part of the state just north of rt. 80
ive not been there but am told its a nice facility.
im sure its at least 800 yds and maybe more.
they hold silloette matches there, not sure of f class.
im told they have informal fun shoots there on weds. a.m. and shoot at clay targets.
might be a good place to practice.